Photoluminescence Properties of GaAs/AlAs Short-Period Superlattices

We have systematically investigated the photoluminescence (PL) properties of (GaAs) 10 /(AlAs) m and (GaAs) l /(AlAs) l superlattices with m =2–20 and l =8–18 monolayers in the wide temperature range from 5 to ∼300 K. Two types of PL bands appear in the superlattices with m ≥6 and l ≤12: the type-I PL between the Γ electrons and the Γ heavy holes of GaAs, and the type-II PL between the X electrons of AlAs and the Γ heavy holes of GaAs. The layer-thickness dependences of the type-I and type-II PL energies in both the (GaAs) 10 /(AlAs) m and (GaAs) l /(AlAs) l superlattices are explained by the results calculated on the basis of an effective-mass approximation with a valence-band-offset ratio of 0.34. We discuss the Γ- X crossover in the conduction band, the anisotropy of the X electron state, and the temperature dependences of the intensities and energies of the type-I and type-II PL bands.